Vaccines for an ageing population
SEATTLE – The world’s population is getting bigger – and older. With the elderly increasingly close to outnumbering their younger counterparts – by 2050, there will be nearly three times more people aged 65 and above than people under four years old – many fear that the burden on government budgets, health- care systems, and economies will become untenable. But there is something we can do to ease that burden: improve the health of the elderly.
As we age, our bodies undergo complex changes that, among other things, progressively weaken our ability to respond to infections and develop immunity (this is called immunosenescence). That is why diseases in older adults tend to be more severe, with a greater impact on quality of life, disability, and mortality, than the same diseases in younger patients.
Put simply, ageing adults’ immune systems need backup. That is where vaccines come in.
Vaccines are most often discussed with regard to young children, who should receive a series of inoculations against childhood illnesses like measles and polio. Childhood vaccinations are one of the greatest medical success stories of the twentieth century, not least because of so- called herd immunity (the indirect protection of entire communities, including those who cannot be immunized for reasons like illness or age, by vaccinating most of their members).
Nothing prohibits adults from taking advantage of the same science. In fact, they would reap far-reaching benefits – including the protection of their family and neighbours – from doing so. Yet few actually do.
Adults need to understand that some of the more common infections to which they are vulnerable are vaccine-preventable. Consider shingles, an infection that can affect anyone who has had chicken pox in their lifetime (that is, 95% of adults worldwide). In the United States, roughly one-third of the population will get shingles at some point in their lives.
A case of shingles may be benign and relatively bearable for someone in his or her thirties. But the disease is far more common among people aged 50 and above – for whom it can be extremely painful. Older adults with shingles may experience chronic discomfort and serious complications that make it difficult to sleep, leave the house, or carry out daily activities. If they have been vaccinated – the Centers for Disease Control and Prevention recommends getting vaccinated at age 60 – they can avoid this painful, sometimes debilitating, condition.
Influenza is another vaccine-preventable disease. While the influenza virus can cause disease in people of all ages, the elderly – those 65 and above – are disproportionately affected, in terms of both death and hospitalization, with the oldest being at the greatest risk.
The problem is that older people are more likely to suffer from one or more underlying health conditions, such as heart disease or diabetes. As a result, they are also more likely to experience more severe influenza-related complications. Systematic analyses among elderly populations found influenza vaccination – which must be delivered annually, to account for constantly emerging new strains – to be not only successful in protecting people from contracting influenza, but also cost- effective.
The list does not end there. Diphtheria, caused by the aerobic gram- positive bacterium Corynebacterium diphtheria, is an acute, toxin- mediated disease that can manifest as an upper respiratory tract infection or a skin infection. Most complications of diphtheria – such as myocarditis ( inflammation of the middle layer of the heart) and neuritis ( inflammation of a peripheral nerve or nerves) – are attributable to the effects of the toxin. The overall fatality rate is 5- 10%, with higher death rates among people younger than five and older than 40.
Tetanus, commonly known as “lockjaw,” is a bacterial disease that affects the nervous system, causing painful tightening of muscles throughout the body. It does not lead to a very high num- ber of deaths among the elderly; but, given that it is preventable, any number higher than zero is unacceptable.
Then there is pertussis. We do not know precisely the extent to which it affects the elderly, because the disease is badly underdiagnosed and underreported in all age groups. But the Advisory Committee on Immunization Practices thinks that the burden of disease is at least 100 times greater than currently reported.
The Tdap vaccine, which protects adults from diphtheria, tetanus, and pertussis, could reduce this burden considerably. Another vaccine, called Td, protects against tetanus and diphtheria, but not pertussis. A Td booster should be given every ten years.
Finally, there is pneumococcal disease, a bacterial infection caused by Streptococcus pneumoniae, which can cause pneumonia, meningitis, or bloodstream infection (sepsis), Depending on which complications occur, symptoms may include cough, abrupt onset of fever, chest pain, chills, shortness of breath, stiff neck, disorientation, and sensitivity to light.
Pneumococcal disease can lead to brain damage, deafness, tissue damage (potentially even requiring the amputation of limbs), and death. In the US alone, pneumococcal pneumonia, bloodstream infections, and meningitis kill tens of thousands of people each year, including 18,000 adults aged 65 years and above. Two main types of pneumococcal vaccine available for older adults – the 23-valent pneumococcal polysaccharide vaccine (PPV23) and the pneumococcal conjugate vaccine (PCV13) – could ameliorate the situation.
Thanks to child immunization programs, fewer children die each year from vaccine-preventable diseases. A similar, concentrated effort is now needed to produce similar benefits for adults, especially the elderly. By viewing vaccination as a lifelong priority, we can help people remain active and productive for as long as possible, benefiting them, their communities, and the world.